There are known units in the prior art designed for their use on vehicles, and more specifically units designed to participate in picking up or releasing a spare wheel in the vehicle, which is disposed beneath the chassis (or on the underside) of the vehicle.
Units of this type comprise a main shaft that extends vertically and passes through a central hole of the wheel, a support in which the wheel is supported and is connected to the main shaft, it being capable of being released in order to make the wheel available, and a cable that is connected at one end to the main shaft and at the other end to a mechanism that is disposed with a shaft of rotation on which the user acts with a tool to pick up or release the wheel.
Units of this type comprise a safety system that consists of an actuator, usually in the shape of a hook, that closes and acts on the main shaft when the wheel has been disposed against the chassis of the vehicle, and is connected to the mechanism by a connection means, so that when an unwanted effect occurs such as the cable breaking, the main shaft comes away and starts to fall but is supported because the hook of the safety actuator supports it. As a result of this there must be an auxiliary safety mechanism that enables the hook to be released from its action with the main shaft, acting on the mechanism, and the user may release the wheel.
U.S. Pat. No. 6,092,790 discloses a unit of this type. In it is disclosed a mechanism for releasing the auxiliary safety device of the spare-wheel-picking up unit, in which in order to release the hook of the safety actuator that is acting on the main shaft, the tool that is used to act on the shaft of rotation of the mechanism is used, it being inserted in a pipe that is found in the mechanism in order to access its shaft. Inside the pipe there is disposed a cam that interrupts the path of the tool, with the result that as the tool passes to reach the shaft of rotation the cam is rotated, the rotation causing the traction of a cable connected at one end to the cam and at the other end to the hook of the safety actuator, which is released from the main shaft.